Multi-objective Optimal Design And Energy Management Of The Small-scale Combined Cooling Heating And Power System

With the worsening energy shortage and environmental pollution,it is critical to develop the distributed energy system.The combined cooling heating and power(CCHP)system can improve the energy efficiency and reduce air pollutant emissions dramatically,thus attracting great attention worldwide.In recent years,micro-CCHP systems have been introduced into relatively small-scale places,such as domestic houses and Commercial buildings,which have already become a new research hotspot.Therefore,this thesis focused on the small-sacle CCHP system,explored and analyzed the performances including thermodynamics,economy and environmental impact.Furthermore,a series of optimal design methods and energy management strategies were proposed,thus improved the comprehensive performance effectively.Meanwhile,the internal energy coupling relationship in the CCHP system was also be revealed and the essence these conflicting objectives was further demonstrated,thereby constructing the theoretical system to promote the development of the CCHP system.Firstly,this thesis demonstrated the configuration and energy flow of a basic CCHP system.In addition,the capacity of the facilities was determined by a general designing method.Meanwhile,the energetic,economic and envirometal performance under following electric demand(FED)mode and following thermal demand(FTD)mode were studied respectively.Moreover,the sensitivity of the performance of the CCHP system to the capacity,technical,economic and emission parameters were also evaluated.Secondly,this thesis designed a small CCHP driven by biogas fuelled internal-combustion engine upon TRNSYS(Transient System Simulation Program)platform considering off-design conditions,explained its energy flow and operation mode;it also established a multi-objective optimization model with integration of energy,economics and environment objectives.The particle swarm optimization algorithm with constraint coefficient was used in calculation,to realize the equipment capacity and operation parameters optimization.The study case simulated by the annual cooling,heating and electrical load of a farmland construction,analyzed the operation performance of the optimized system,as well as compared the property difference between the biogas CCHP system and the natural gas CCHP system.Based on the above configuration,a multi-objective optimization model is proposed,aiming to maximize the energy-saving ratio and minimize the energy costs of a micro-CCHP system consisting of an absorption and electric chiller.The Non-dominated Sorting Genetic Algorithm-II(NSGA-II)is employed to identify a series of compromised optimal operation strategies with different operational parameters,using a co-simulation optimization platform.Moreover,the characteristics analysis is further made to reveal the energy coupling between these conflicting objectives in the operation of CCHP system.Then,a CCHP system with the storage unit and the electric chiller was designed.A multi-objective model considering the energetic,economic and environmental benefits has been built,aiming to optimize the rated power of the power generation unit(PGU),the capacity of storage unit,the electric chilling ratio and the on-off coefficient of the PGU.Moreover,NSGA-? was adopted to solve the optimal model,thus obtaining multiple optimal designing combinations focusing on different performance.The energy saving rate was chosen as an example inorder to reveal the inherent effects of all designing parameters on the system performance.Furthermore,the coupling relationships between these objectives were quantified,thereby providing the reliable method of balancing the benefits of all participants for the decision-makers in the designing process.Meanwhile,a micro-CCHP system with heat storage tank was built and an economic optimization model consisting of depreciation,energy and environment costs was proposed.Based on the co-simulation optimization platform combining TRNSYS and Matlab,genetic algorithm was employed to identify optimal operation strategies.A simulation case study was performed using daily load of an office building in summer and in winter.Variations of power and cost were analyzed scientifically.This methodology provided theoretical basis and platform support for optimal operation study of CCHP system.At last,a CCHP experimental system,with multi-energy conversion units such as the absorption chiller and the electric heat pump,was designed based on the novel PGU developed by Shandong University and Weichai Power Co.,Ltd,aiming to utilize the biogas and solar power.This system could provide the application platform for vertifying the above optimal methods.In general,the conclusions of this thesis provide effective methods for the configuration design and operation management of small-scale CCHP system,which could promote the development of the distributed generation.